Mask



FIG. 1 is a perspective view of a mask showing our new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines immediately adjacent the claimed areas represent the bounds of the claimed design while all other broken lines are directed to environment that form no part of the claimed design. 

CLAIM The ornamental design for a mask, as shown and described. 